The present invention relates to novel galectin sequences and use thereof in treatment or diagnosis of arthritis and other chronic inflammatory diseases.
Rheumatoid Arthritis (RA) is a chronic, systemic inflammatory disease primarily involving the joints. It affects 1-3% of the population with a female to male ratio of 3:1. Constitutional symptoms may include malaise, fever and weight loss. The disease characteristically begins in the small joints of the hands and feet, usually progressing in a centripetal and symmetric fashion. Deformation of joints and disability are very common, but the disease may also decrease expected life span by an average of ˜9 years in the more active forms. Extra-articular manifestations of the rheumatoid process may cause significant morbidity and include vasculitis, atrophy of the skin and muscle, subcutaneous nodules, lymphadenopathy, splenomegaly and leukopenia, neuropathy, cervical myelopathy, ophthalmic complications, Sjogren syndrome, lung and heart involvement and amyloidosis.
The inflammation of the synovial joints characterizing RA is the result of hyperplasia of synovial fibroblasts and infiltration of lymphocytes, macrophages and plasma cells, all of which manifest signs of activation. These cells proliferate abnormally, invade bone and cartilage, produce an elevated amount of pro-inflammatory cytokines, metalloproteinases and trigger osteoclast formation and activation. Some of the pathophysiological consequences of the disease are explained by inadequate apoptosis, which may promote the survival of autoreactive T cells, macrophages or synovial fibroblasts [Rabinovich G. A., Mem Inst Oswaldo Cruz., 95:225, (2000)].
Selective therapeutic targeting of pathological cells, such as inflammatory cells is a major challenge for modern medicine. Differences in cell surface molecules or signal transduction pathways between pathological cells and their normal counterparts can be used as a handle for selective destruction of the former. Unfortunately, the existence of such discrete target entities in pathological cells is not an obvious phenomenon.
Discrimination between “harmful” inflammatory cells, involved in self-destruction, and inflammatory cells engaged in the eradication of microorganisms is complicated, because there is no indication that the two cell types differ chemically or biologically. The discriminatory elements might be found in the T cell receptor (TCR) of those cells initiating the inflammatory cascade or in the corresponding major histocompatibility (MHC) sequences of antigen presenting cells (APCs), which bind the relevant peptide. Unfortunately, targeting of TCR or MHC molecules would be effective only at the initial phase of autoimmune diseases, when the symptoms are still undetectable. Consequently, in many cases this approach may be impractical.
A different tactic is to target pro-inflammatory molecules that are involved in more progressive stages of the process, when there is a non-specific influx of leukocytes, attracted by chemokines and activated by cytokines. Indeed, it has been shown that autoimmune diseases can be controlled by targeting inflammation-supportive molecules, such as selecting, integrins, IL-12, TNFα and NFkB, using specific antibodies or anti-sense oligonucleotide [Taylor P. C., Curr. Pharm. Des., 9:1095, (2003); Kevorkov N. N. and Futlik D. M., Russ. J. Immunol., 5:5, (2000); Louie S. G., et al. Am. J. Health Syst. Pharm. 60:346, (2003)].
However, the same molecules are also involved in essential physiological functions and, therefore, it is unpredictable when and how the price of such “nonspecific” therapy will be exacted.
There is thus a widely recognized need for restricted targeting inflammation-supportive molecules and it would be highly advantageous to identify pro-inflammatory molecules, involved in a relatively late phase of the process that displays sufficient chemical diversity to allow restricted targeting. The novel galectin isoforms presented here may meet these requirements.
Galectins comprise a family of proteins that are widely expressed in mammals. All galectins share the ability to bind β-galactosides through an evolutionarily conserved sequence motif in the carbohydrate-binding site (1). They have a cytoplasmic or nuclear localization and despite of lack of signal peptide, they can be externalized as soluble proteins by non-classical secretory mechanisms (2, 3). In mammals, ten galectins have been characterized (3, 4). Two groups of galectins are distinguished according to the number of lectin domains. Most of them, including galectin-1, 2, 3, 5, 7 and 10, have a single lectin domain. Galectin-4, 6, 8 and 9 belong to the second group and are characterized by two lectin domains linked by a hinged peptide (4-7).
The exact role(s) of galectins is not clearly established, but they are suspected to modulate several cellular functions such as physiological (8) and malignant cell adhesion, cell proliferation (9), apoptosis (10), metastasis seeding (11) and immune function (12, 13). They have also been described as nuclear proteins (14) possibly involved in pre-messenger RNA splicing (15, 16). Expression analysis has revealed a broad distribution in healthy tissues for galectin-1, 3, 4, 8 and 9, while galectin-2, 5, 6 or 7 are restricted mainly to one specific tissue (such as lung, prostate etc., 16 17). Differential expression of these proteins has been well documented in the literature in healthy tissues or in tumor cells (9, 11, 18).
The present inventors have previously uncovered that galectin-8 and variants thereof are capable of reducing the inflammatory response in human synovial tissue due to their ability to inhibit the release of the pro-inflammatory cytokines TNF-α and IL-1β, to increase the production of the anti-inflammatory cytokine IL-1ra and to induce apoptosis in synovial fluid cells (see PCT Appl. No. IL03/00960).
While reducing the present invention to practice, the present inventors have identified novel isoforms of human galectins which are specific to synovial fluid cells of RA patients. Thus, compositions and methods containing these novel galectins may be utilized for treatment and diagnostics of RA, or restricted targeting of inflammation-supportive molecules.